{

uint64_t m_canary;

const int m_implementation;

const int m_bits;

Sketch(int implementation, int bits) : m_implementation(implementation), m_bits(bits) {}

void Ready() { m_canary = 0x6d496e536b65LU; }

void Check() const { if (m_canary != 0x6d496e536b65LU) abort(); }

void UnReady() { m_canary = 1; }

int Implementation() const { return m_implementation; }

int Bits() const { return m_bits; }

virtual ~Sketch() {}

virtual size_t Syndromes() const = 0;

virtual void Init(int syndromes) = 0;

virtual void Add(uint64_t element) = 0;

virtual void Serialize(unsigned char*) const = 0;

virtual void Deserialize(const unsigned char*) = 0;

virtual size_t Merge(const Sketch* other_sketch) = 0;

virtual void SetSeed(uint64_t seed) = 0;

virtual int Decode(int max_count, uint64_t* roots) const = 0;